Class java.lang.StringBuffer





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Class java.lang.StringBuffer


java.lang.Object
|
+----java.lang.StringBuffer



public final class StringBuffer
extends Object
implements Serializable

A string buffer implements a mutable sequence of characters.

String buffers are safe for use by multiple threads. The methods
are synchronized where necessary so that all the operations on any
particular instance behave as if they occur in some serial order.

String buffers are used by the compiler to implement the binary
string concatenation operator +. For example, the code:

x = "a" + 4 + "c"

is compiled to the equivalent of:

x = new StringBuffer().append("a").append(4).append("c")
.toString()

The principal operations on a StringBuffer are the
append and insert methods, which are
overloaded so as to accept data of any type. Each effectively
converts a given datum to a string and then appends or inserts the
characters of that string to the string buffer. The
append method always adds these characters at the end
of the buffer; the insert method adds the characters at
a specified point.

For example, if z refers to a string buffer object
whose current contents are "start", then
the method call z.append("le") would cause the string
buffer to contain "startle", whereas
z.insert(4, "le") would alter the string buffer to
contain "starlet".

Every string buffer has a capacity. As long as the length of the
character sequence contained in the string buffer does not exceed
the capacity, it is not necessary to allocate a new internal
buffer array. If the internal buffer overflows, it is
automatically made larger.


See Also:
ByteArrayOutputStream, String








StringBuffer()
Constructs a string buffer with no characters in it and an
initial capacity of 16 characters.

StringBuffer(int)
Constructs a string buffer with no characters in it and an
initial capacity specified by the length argument.

StringBuffer(String)
Constructs a string buffer so that it represents the same
sequence of characters as the string argument.






append(boolean)
Appends the string representation of the boolean
argument to the string buffer.

append(char)
Appends the string representation of the char
argument to this string buffer.

append(char[])
Appends the string representation of the char array
argument to this string buffer.

append(char[], int, int)
Appends the string representation of a subarray of the
char array argument to this string buffer.

append(double)
Appends the string representation of the double
argument to this string buffer.

append(float)
Appends the string representation of the float
argument to this string buffer.

append(int)
Appends the string representation of the int
argument to this string buffer.

append(long)
Appends the string representation of the long
argument to this string buffer.

append(Object)
Appends the string representation of the Object
argument to this string buffer.

append(String)
Appends the string to this string buffer.

capacity()
Returns the current capacity of the String buffer.

charAt(int)
Returns the character at a specific index in this string buffer.

ensureCapacity(int)
Ensures that the capacity of the buffer is at least equal to the
specified minimum.

getChars(int, int, char[], int)
Characters are copied from this string buffer into the
destination character array dst.

insert(int, boolean)
Inserts the string representation of the boolean
argument into this string buffer.

insert(int, char)
Inserts the string representation of the char
argument into this string buffer.

insert(int, char[])
Inserts the string representation of the char array
argument into this string buffer.

insert(int, double)
Inserts the string representation of the double
argument into this string buffer.

insert(int, float)
Inserts the string representation of the float
argument into this string buffer.

insert(int, int)
Inserts the string representation of the second int
argument into this string buffer.

insert(int, long)
Inserts the string representation of the long
argument into this string buffer.

insert(int, Object)
Inserts the string representation of the Object
argument into this string buffer.

insert(int, String)
Inserts the string into this string buffer.

length()
Returns the length (character count) of this string buffer.

reverse()
The character sequence contained in this string buffer is
replaced by the reverse of the sequence.

setCharAt(int, char)
The character at the specified index of this string buffer is set
to ch.

setLength(int)
Sets the length of this String buffer.

toString()
Converts to a string representing the data in this string buffer.







StringBuffer

public StringBuffer()


Constructs a string buffer with no characters in it and an
initial capacity of 16 characters.



StringBuffer

public StringBuffer(int length)


Constructs a string buffer with no characters in it and an
initial capacity specified by the length argument.


Parameters:
length - the initial capacity.
Throws: NegativeArraySizeException
if the length
argument is less than 0.



StringBuffer

public StringBuffer(String str)


Constructs a string buffer so that it represents the same
sequence of characters as the string argument. The initial
capacity of the string buffer is 16 plus the length
of the string argument.


Parameters:
str - the initial contents of the buffer.







length

public int length()


Returns the length (character count) of this string buffer.


Returns:
the number of characters in this string buffer.



capacity

public int capacity()


Returns the current capacity of the String buffer. The capacity
is the amount of storage available for newly inserted
characters; beyond which an allocation will occur.


Returns:
the current capacity of this string buffer.



ensureCapacity

public synchronized void ensureCapacity(int minimumCapacity)


Ensures that the capacity of the buffer is at least equal to the
specified minimum.
If the current capacity of this string buffer is less than the
argument, then a new internal buffer is allocated with greater
capacity. The new capacity is the larger of:

The minimumCapacity argument.
Twice the old capacity, plus 2.

If the minimumCapacity argument is nonpositive, this
method takes no action and simply returns.


Parameters:
minimumCapacity - the minimum desired capacity.



setLength

public synchronized void setLength(int newLength)


Sets the length of this String buffer.
If the newLength argument is less than the current
length of the string buffer, the string buffer is truncated to
contain exactly the number of characters given by the
newLength argument.

If the newLength argument is greater than or equal
to the current length, sufficient null characters
('\u0000') are appended to the string buffer so that
length becomes the newLength argument.

The newLength argument must be greater than or equal
to 0.


Parameters:
newLength - the new length of the buffer.
Throws: StringIndexOutOfBoundsException
if the
newLength argument is invalid.
See Also:
length



charAt

public synchronized char charAt(int index)


Returns the character at a specific index in this string buffer.

The first character of a string buffer is at index
0, the next at index 1, and so on, for
array indexing.

The index argument must be greater than or equal to
0, and less than the length of this string buffer.


Parameters:
index - the index of the desired character.
Returns:
the character at the specified index of this string buffer.
Throws: StringIndexOutOfBoundsException
if the index is invalid.
See Also:
length



getChars

public synchronized void getChars(int srcBegin,
int srcEnd,
char dst[],
int dstBegin)


Characters are copied from this string buffer into the
destination character array dst. The first character to
be copied is at index srcBegin; the last character to
be copied is at index srcEnd-1. The total number of
characters to be copied is srcEnd-srcBegin. The
characters are copied into the subarray of dst starting
at index dstBegin and ending at index:

dstbegin + (srcEnd-srcBegin) - 1



Parameters:
srcBegin - start copying at this offset in the string buffer.
srcEnd - stop copying at this offset in the string buffer.
dst - the array to copy the data into.
dstBegin - offset into dst.
Throws: StringIndexOutOfBoundsException
if there is an invalid
index into the buffer.



setCharAt

public synchronized void setCharAt(int index,
char ch)


The character at the specified index of this string buffer is set
to ch.

The offset argument must be greater than or equal to
0, and less than the length of this string buffer.


Parameters:
index - the index of the character to modify.
ch - the new character.
Throws: StringIndexOutOfBoundsException
if the index is invalid.
See Also:
length



append

public synchronized StringBuffer append(Object obj)


Appends the string representation of the Object
argument to this string buffer.

The argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then appended to this string buffer.


Parameters:
obj - an Object.
Returns:
this string buffer.
See Also:
valueOf, append



append

public synchronized StringBuffer append(String str)


Appends the string to this string buffer.

The characters of the String argument are appended, in
order, to the contents of this string buffer, increasing the
length of this string buffer by the length of the argument.


Parameters:
str - a string.
Returns:
this string buffer.



append

public synchronized StringBuffer append(char str[])


Appends the string representation of the char array
argument to this string buffer.

The characters of the array argument are appended, in order, to
the contents of this string buffer. The length of this string
buffer increases by the length of the argument.


Parameters:
str - the characters to be appended.
Returns:
this string buffer.



append

public synchronized StringBuffer append(char str[],
int offset,
int len)


Appends the string representation of a subarray of the
char array argument to this string buffer.

Characters of the character array str, starting at
index offset, are appended, in order, to the contents
of this string buffer. The length of this string buffer increases
by the value of len.


Parameters:
str - the characters to be appended.
offset - the index of the first character to append.
len - the number of characters to append.
Returns:
this string buffer.



append

public StringBuffer append(boolean b)


Appends the string representation of the boolean
argument to the string buffer.

The argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then appended to this string buffer.


Parameters:
b - a boolean.
Returns:
this string buffer.
See Also:
valueOf, append



append

public synchronized StringBuffer append(char c)


Appends the string representation of the char
argument to this string buffer.

The argument is appended to the contents of this string buffer.
The length of this string buffer increases by 1.


Parameters:
ch - a char.
Returns:
this string buffer.



append

public StringBuffer append(int i)


Appends the string representation of the int
argument to this string buffer.

The argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then appended to this string buffer.


Parameters:
i - an int.
Returns:
this string buffer.
See Also:
valueOf, append



append

public StringBuffer append(long l)


Appends the string representation of the long
argument to this string buffer.

The argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then appended to this string buffer.


Parameters:
l - a long.
Returns:
this string buffer.
See Also:
valueOf, append



append

public StringBuffer append(float f)


Appends the string representation of the float
argument to this string buffer.

The argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then appended to this string buffer.


Parameters:
f - a float.
Returns:
this string buffer.
See Also:
valueOf, append



append

public StringBuffer append(double d)


Appends the string representation of the double
argument to this string buffer.

The argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then appended to this string buffer.


Parameters:
d - a double.
Returns:
this string buffer.
See Also:
valueOf, append



insert

public synchronized StringBuffer insert(int offset,
Object obj)


Inserts the string representation of the Object
argument into this string buffer.

The second argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then inserted into this string buffer at the indicated
offset.

The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.


Parameters:
offset - the offset.
b - an Object.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.
See Also:
valueOf, insert, length



insert

public synchronized StringBuffer insert(int offset,
String str)


Inserts the string into this string buffer.

The characters of the String argument are inserted, in
order, into this string buffer at the indicated offset. The length
of this string buffer is increased by the length of the argument.

The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.


Parameters:
offset - the offset.
str - a string.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.
See Also:
length



insert

public synchronized StringBuffer insert(int offset,
char str[])


Inserts the string representation of the char array
argument into this string buffer.

The characters of the array argument are inserted into the
contents of this string buffer at the position indicated by
offset. The length of this string buffer increases by
the length of the argument.


Parameters:
offset - the offset.
ch - a character array.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.



insert

public StringBuffer insert(int offset,
boolean b)


Inserts the string representation of the boolean
argument into this string buffer.

The second argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then inserted into this string buffer at the indicated
offset.

The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.


Parameters:
offset - the offset.
b - a boolean.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.
See Also:
valueOf, insert, length



insert

public synchronized StringBuffer insert(int offset,
char c)


Inserts the string representation of the char
argument into this string buffer.

The second argument is inserted into the contents of this string
buffer at the position indicated by offset. The length
of this string buffer increases by one.

The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.


Parameters:
offset - the offset.
ch - a char.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.
See Also:
length



insert

public StringBuffer insert(int offset,
int i)


Inserts the string representation of the second int
argument into this string buffer.

The second argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then inserted into this string buffer at the indicated
offset.

The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.


Parameters:
offset - the offset.
b - an int.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.
See Also:
valueOf, insert, length



insert

public StringBuffer insert(int offset,
long l)


Inserts the string representation of the long
argument into this string buffer.

The second argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then inserted into this string buffer at the indicated
offset.

The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.


Parameters:
offset - the offset.
b - a long.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.
See Also:
valueOf, insert, length



insert

public StringBuffer insert(int offset,
float f)


Inserts the string representation of the float
argument into this string buffer.

The second argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then inserted into this string buffer at the indicated
offset.

The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.


Parameters:
offset - the offset.
b - a float.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.
See Also:
valueOf, insert, length



insert

public StringBuffer insert(int offset,
double d)


Inserts the string representation of the double
argument into this string buffer.

The second argument is converted to a string as if by the method
String.valueOf, and the characters of that
string are then inserted into this string buffer at the indicated
offset.

The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.


Parameters:
offset - the offset.
b - a double.
Returns:
this string buffer.
Throws: StringIndexOutOfBoundsException
if the offset is invalid.
See Also:
valueOf, insert, length



reverse

public synchronized StringBuffer reverse()


The character sequence contained in this string buffer is
replaced by the reverse of the sequence.


Returns:
this string buffer.



toString

public String toString()


Converts to a string representing the data in this string buffer.
A new String object is allocated and initialized to
contain the character sequence currently represented by this
string buffer. This String is then returned. Subsequent
changes to the string buffer do not affect the contents of the
String.


Returns:
a string representation of the string buffer.
Overrides:
toString in class Object




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